This lecture considers the arrival of the Moors in Spain in 711, their fast invasion and the process of the building of the Mosque at Córdoba. It will outline the different building stages, the establishing of a Caliphate in Cordoba and highlight changes in regimes over the 800 years in which the Moors remained in Spain. This period of fertile growth in the arts and sciences will be discussed with reference to poetry and philosophy. The extraordinary beauty and serenity of the Mosque will be unravelled in such a way that visitors will also understand the subtle secrets and messages hidden in the architectural decorations and Arabic inscriptions. The building of the church in the centre of the Mosque will be discussed within the light of a fusion of cultures, considering whether the Christians dispelled or preserved the Moors. It will end with a discussion of the meaning of the building today.